I think each character in the game including feral chaos gets 9 dlc outfits but I don't think the characters have that many official DLCs so there should be some room to add some custom DLCs still of your choosing without overwriting I use a problem called
DDFF DLC Toolkit there's a link below note you can also use this add Custom DLCs over Alt outfits 1 and 2 as well.
Another quick note, still be careful not to overwrite you Official and Custom DLCs while using this okay, be warned but I'm sure you got this.

When Dissidia Forums went down allot of tutorials with it also disappeared too, it's only hard right now, because theres not much information on it anymore...
And we're new at it, eventually will get the hang of it.